1. Field of the Invention
This invention relates generally to cutting apparatus and more specifically to nibblers adapted to cut sheet metal.
2. Description of the Prior Art
The nibblers of the prior art have included a source of power enclosed in a housing for reciprocating a punch relative to a die between a cutting stroke and a return stroke. Sheet metal moved relative to the punch and die has been nibbled away by action of the punch and die to cut the sheet metal. Means has also been provided on the side of the sheet metal opposite the die for stripping the sheet metal from the punch during the return stroke.
The dies in the prior art devices have been elaborate and complex, often formed from a single piece of material. These dies have been constructed for disposition in a single position relative to the punch. Thus, alignment of the punch and die has been a significant problem.
In some nibblers of the prior art, the die surface has been defined on the same side of the sheet metal as the housing. In such embodiments, the punch has been aligned with the die by guide members on both sides of the cutting surface. The guide members on the side of the cutting surface opposite the housing have been particularly large and therefore have required starting holes of significant size in order to make interior cuts. Large starting holes are undesirable where small internal cuts are to be made.
In other nibblers of the prior art, the cutting surface of the die has been defined on the side of the sheet metal opposite the source of power. These die assemblies have also been relatively large, therefore necessitating starting holes of significant size.
The portions connecting the guide members on opposite sides of the sheet metal must necessarily ride in the cut made by the punch. With this disposition, these connecting portions have a considerable effect on the sharpness of a corner which can be cut. In the past, these portions have been relatively large and often have been displaced from the punch so that the sharpness of corners has been quite limited.
It is often desirable to make square interior cuts in a piece of sheet metal. This generally requires a punch and associated die channel having a rectangular configuration. In the past, such die channels have been cut from a single piece of material by boring the material. This process is particularly expensive so that rectangular punches and dies have been provided only on very elaborate and expensive apparatus.